Experimental investigation on the hydrothermal attributes of MWCNT/water nanofluid in the shell-side of shell and semi-circular tubes heat exchanger

Abstract

This study experimentally examines the hydrothermal performance attributes of a horizontal shell and semi-circular tubes (SCTs) heat exchanger of a counter-flow configuration. The tests are done by employing cold pure water or Multi-Walled Carbon Nanotube (MWCNT)/water nanofluid in the shell-side. The SCTs spacing ratio (0.157 ≤ δ ≤ 0.472), MWCNT volume concentration (0 ≤ φ ≤ 0.5%), and the operational conditions of the shell-side (3351 ≤ Resh ≤ 13461, 4.85 ≤ Prsh ≤ 7.54) are the key parameters throughout this study. Compared with the case of employing complete circular tubes and pure water in the shell-side, the results state that splitting the internal tubes and/or adding MWCNT increase both the shell-average Nusselt number (Nu¯sh) and Fanning friction factor (fsh), by average increases of 44.4–106.2% and 7.1–29.6%, respectively, when δ increases from 0.157 to 0.472, and with average increases of 8.2–41.8% and 5.9–33.6%, respectively, when φ increases from 0.1% to 0.5%. The hydrothermal performance index (HTPI) is assessed to compare the performance of the heat exchanger with SCTs and with/without MWCNT to that of the case of circular tubes and pure water. The results record that incorporating both SCTs (δ = 0.472) and MWCNT (φ = 0.5%) provides the highest HTPI; 2.46, and it is reduced by their reduction. Finally, correlations for Nu¯sh, fsh, and HTPI are proposed.